[Top][All Lists]
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PATCH] Zero some registers in linux_trampoline
From: |
Colin Watson |
Subject: |
[PATCH] Zero some registers in linux_trampoline |
Date: |
Tue, 24 Aug 2010 15:53:14 +0100 |
User-agent: |
Mutt/1.5.18 (2008-05-17) |
linux/Documentation/x86/boot.txt specifies that:
At entry, the CPU must be in 32-bit protected mode with paging
disabled; a GDT must be loaded with the descriptors for selectors
__BOOT_CS(0x10) and __BOOT_DS(0x18); both descriptors must be 4G flat
segment; __BOOS_CS must have execute/read permission, and __BOOT_DS
must have read/write permission; CS must be __BOOT_CS and DS, ES, SS
must be __BOOT_DS; interrupt must be disabled; %esi must hold the base
address of the struct boot_params; %ebp, %edi and %ebx must be zero.
In the linux_trampoline used in a 64-bit EFI target, we jump to the
contents of %edi, so that at least is certainly non-compliant with the
specification above. I don't know about %ebp and %ebx but it would be
good to make sure.
How about the following patch?
2010-08-24 Colin Watson <address@hidden>
* loader/i386/linux_trampoline.S (cont2): Zero %ebp, %edi, and %ebx
before jumping to the kernel, per the Linux 32-bit boot protocol
specification.
=== modified file 'loader/i386/linux_trampoline.S'
--- loader/i386/linux_trampoline.S 2009-06-10 21:04:23 +0000
+++ loader/i386/linux_trampoline.S 2010-08-24 14:50:21 +0000
@@ -93,8 +93,12 @@ cont2:
.code32
mov %ebx, %esi
+ mov %edi, %ecx
+ xor %ebp, %ebp
+ xor %edi, %edi
+ xor %ebx, %ebx
- jmp *%edi
+ jmp *%ecx
/* GDT. */
.p2align 4
--
Colin Watson address@hidden
[Prev in Thread] |
Current Thread |
[Next in Thread] |
- [PATCH] Zero some registers in linux_trampoline,
Colin Watson <=